Although this invention is especially designed for use in the aircraft and aerospace industries, it will be appreciated that it may also be employed in nautical and land vehicle applications, such as rail and/or automotive applications.
In the aircraft and aerospace industries, stiffened panels, and especially stringer-stiffened panels have become standard as a light-weight construction solution. Indeed, typically more than 90% of the fuselage or the outer “skin” of modern passenger aircraft is designed as stringer-stiffened panels. In this regard, a “stringer” is a stiffening member which increases the out-of-plane bending stiffness of a structural panel or area member. With stringers, a panel is reinforced against global buckling under compression and shear loading. The resulting instability and collapse loading of the panel member is thereby shifted to higher loading with a lower structural weight penalty compared to simply thickening the panel member itself. Stringers also limit the dimensions of any buckling in the panel member or skin to localized regions between the stringers (i.e., the “skin bays”), to provide so-called local buckling. By reducing buckling field dimensions (i.e., the size of the skin bays), the buckling strength of the panel member or skin is increased.
While design efforts are continually directed to reducing the mass of an aircraft in order to optimize fuel consumption, it nevertheless remains critical that strength and safety of the aircraft structure is not compromised and that the testing standards are still met.